This proposal addresses issues relevant to normal cell growth and to disease: the spatial organization within the nucleus, and how the nucleus communicates with the cytoplasm and the cell exterior. The focus is on the relationship between the organization of the genome and the processing and export of mRNAs. The movement of mRNAs through the nucleoplasm and out of the nucleus to cytoplasmic locations is an elaborately orchestrated and regulated process. The pathway of mRNA export includes: proper processing, packaging into protein-RNA complexes, targeting and movement through the nuclear pore complex (NPC) and release into the cytoplasm for translation. In some cases, mRNAs are further localized within the cytoplasm. This proposal focuses on the spatial organization of the genome with respect to its interactions with the NPC, nuclear export factors, RNA binding proteins, and the processing and movement of mRNAs out of the nucleus. The Specific Aims are designed to determine: 1) the requirements for gene movement with respect to the nuclear export machinery;2) the connection between intranuclear gene location, mRNA export and cytoplasmic mRNA location;3) the interaction of the genome with the nuclear export machinery;and 4) the identification and specificity of recruitment of RNA binding proteins important for mRNA processing and export. The regulation of mRNA dynamics is key to certain genetic diseases, the function of some viral proteins, the response of cells to growth stimuli, and, in some cases, the basis for drug action. We have come to appreciate the complex interplay between gene expression, nuclear organization and transport. This inherent complexity can affect growth status and disease states. Moreover, defects in mRNA processing are associated with a number of diseases including metastatic cancers, muscular dystrophy and amyotrophic lateral sclerosis. The experiments proposed in this grant will not only lead to new basic insights but also to new ways to analyze on a genome-wide level the situation in genetically defective cells and certain cancers.